Systems for vibration cancellation in a lidar system

ABSTRACT

A scanning lidar system includes an external frame, an internal frame attached to the external frame by vibration-isolation mounts, and an electro-optic assembly movably attached to the internal frame and configured to be translated with respect to the internal frame during scanning operation of the scanning lidar system.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 62/438,735, filed on Dec. 23, 2016, the content of whichis incorporated by reference in its entirety.

The following three U.S. Patent Applications (including this one) arebeing filed concurrently, and the entire disclosures of the otherapplications are incorporated by reference into this application for allpurposes:

application Ser. No. 15/841,114, filed Dec. 13, 2017, entitled “SCANNINGAPPARATUSES AND METHODS FOR A LIDAR SYSTEM,” now U.S. Pat. No.10,690,754,

application Ser. No. 15/841,121, filed Dec. 13, 2017, entitled “SYSTEMSFOR VIBRATION CANCELLATION IN A LIDAR SYSTEM”, and

application Ser. No. 15/841,125, filed Dec. 13, 2017, entitled “MOUNTINGAPPARATUSES FOR OPTICAL COMPONENTS IN A SCANNING LIDAR SYSTEM,” now U.S.Pat. No. 10,845,466.

BACKGROUND

Three-dimensional sensors can be applied in autonomous vehicles, drones,robotics, security applications, and the like. Scanning lidar sensorsmay achieve high angular resolutions appropriate for such applicationsat an affordable cost. However, scanning lidar sensors may besusceptible to external vibration sources as well as internal vibrationsources. For example, when applied in an autonomous vehicle, scanninglidar sensors may be exposed to external vibrations from uneven roads,road noise, and engine noise. Internal noise from the scanning mechanismmay also interfere with the operations of scanning lidars. Therefore, itmay be desirable to include systems for mitigating vibrations and activevibration management systems in scanning lidar sensors.

SUMMARY

According to some embodiments of the present invention, a scanning lidarsystem includes a fixed frame, a first platform flexibly attached to thefixed frame, and a lens assembly. The lens assembly includes a firstlens and a second lens mounted on the first platform. The first lensdefines a first optical axis in a first direction and a first focalplane. The second lens defines a second optical axis substantiallyparallel to the first optical axis and a second focal plane. The firstplatform is configured to be translated in a first plane substantiallyperpendicular to the first direction. The scanning lidar system furtherincludes a second platform flexible attached to the fixed frame andseparated from the first platform along the first direction. Thescanning lidar system further includes an electro-optic assembly thatincludes a first laser source and a first photodetector mounted on thesecond platform. The second platform is configured to be translated in asecond plane substantially perpendicular to the first direction. Thefirst laser source lies substantially at the focal plane of the firstlens, and the first photodetector lies substantially at the focal planeof the second lens. The first laser source and the first photodetectorare spaced apart from each other on the second platform so as to beoptically conjugate with respect to each other. The scanning lidarsystem further includes a drive mechanism mechanically coupled to thefirst platform and the second platform and configured to translate thefirst platform and the second platform with respect to the fixed frame.The scanning lidar system further includes a controller coupled to thedrive mechanism. The controller is configured to translate the firstplatform to a plurality of first positions in the first plane throughthe drive mechanism, and translate the second platform to a plurality ofsecond positions in the second plane through the drive mechanism, suchthat a motion of the second platform is substantially opposite to amotion of the first platform. Each respective second positioncorresponds to a respective first position.

According to some other embodiments of the present invention, a methodof three-dimensional imaging using a scanning lidar system includestranslating a lens assembly to a plurality of first positions. The lensassembly includes a first lens defining a first optical axis in a firstdirection and a first focal plane, and a second lens defining a secondoptical axis substantially parallel to the first optical axis and asecond focal plane. The method may further include translating anelectro-optic assembly to a plurality of second positions. Theelectro-optic assembly moves in a direction substantially opposite tomotion of the lens assembly. Each respective second position correspondsto a respective first position of the lens assembly. The electro-opticassembly may include a first laser source positioned substantially atthe first focal plane of the first lens, and a first photodetectorpositioned substantially at the second focal plane of the second lens.The first laser source and the first photodetector may be spaced apartfrom each other so as to be optically conjugate with respect to eachother. The method may further include, at each of the plurality ofsecond positions, emitting, using the first laser source, a laser pulse,and collimating and directing, using the first lens, the laser pulsetowards one or more objects. A portion of the laser pulse may bereflected off of the one or more objects. The method may further includereceiving and focusing, using the second lens, the portion of the laserpulse reflected off of the one or more objects to the firstphotodetector, detecting, using the first photodetector, the portion ofthe laser pulse, and determining, using a processor, a time of flightbetween emitting the laser pulse and detecting the portion of the laserpulse. The method may further include constructing a three-dimensionalimage of the one or more objects based on the determined times offlight.

According to some embodiments of the present invention, a scanning lidarsystem includes an external frame, an internal frame attached to theexternal frame by vibration-isolation mounts, and an electro-opticassembly movably attached to the internal frame and configured to betranslated with respect to the internal frame during scanning operationof the scanning lidar system.

According to some other embodiments of the present invention, a scanninglidar system includes an external frame, an internal frame attached tothe external frame by vibration-isolation mounts, an electro-opticassembly movably attached to the internal frame and configured to betranslated with respect to the internal frame during scanning operationof the scanning lidar system, a counterweight movably attached to theinternal fame, a driving mechanism mechanically coupled to thecounterweight, a first sensor couple to the internal frame for measuringan amount of motion of the internal frame, and a controller coupled tothe first sensor and the driving mechanism. The controller is configuredto cause a motion of the counterweight with respect to the internalframe based on the amount of motion of the internal frame measured bythe first sensor.

According to some embodiments of the present invention, a scanning lidarsystem includes an external frame, an internal frame attached to theexternal frame by vibration-isolation mounts, an electro-optic assemblymovably attached to the internal frame and configured to be translatedwith respect to the internal frame during scanning operation of thescanning lidar system, a counterweight movably attached to the internalfame, a driving mechanism mechanically coupled to the counterweight, afirst sensor couple to the external frame for measuring an amount ofmotion of the external frame, and a controller coupled to the firstsensor and the driving mechanism. The controller is configured to causea motion of the counterweight with respect to the internal frame basedon the amount of motion of the external frame measured by the firstsensor.

According to some embodiments of the present invention, a scanning lidarsystem includes a first lens having a first lens center andcharacterized by a first optical axis and a first surface of best focus,and a second lens having a second lens center and characterized by asecond optical axis substantially parallel to the first optical axis.The scanning lidar system further includes a platform separated from thefirst lens and the second lens along the first optical axis, and anarray of laser sources mounted on the platform. Each laser source of thearray of laser sources has an emission surface lying substantially atthe first surface of best focus of the first lens and positioned at arespective laser position. The scanning lidar system further includes anarray of photodetectors mounted on the platform. Each photodetector ofthe array of photodetectors is positioned at a respective photodetectorposition that is optically conjugate with a respective laser position ofa corresponding laser source.

According to some embodiments of the present invention, a scanning lidarsystem includes a first lens having a lens center and characterized by afirst optical axis and a first surface of best focus, a platformseparated from the first lens along the first optical axis, and an arrayof laser sources mounted on the platform. Each laser source of the arrayof laser sources has an emission surface lying substantially at thefirst surface of best focus of the first lens and positioned at arespective laser position. The scanning lidar system further includes anarray of photodetectors mounted on the platform. Each photodetector ofthe array of photodetectors is positioned at a respective photodetectorposition that is optically conjugate with a respective laser position ofa corresponding laser source.

According to some embodiments of the present invention, a scanning lidarsystem includes a lens characterized by a lens center and an opticalaxis, a platform separated from the lens along the optical axis, and anarray of laser sources mounted on the platform. Each laser source of thearray of laser sources is positioned at a respective laser position, anda normal of an emission surface of each laser source pointssubstantially toward the lens center. The scanning lidar system furtherincludes an array of photodetectors mounted on the platform. Eachphotodetector of the array of photodetectors is positioned at arespective photodetector position that is optically conjugate with arespective laser position of a corresponding laser source.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates schematically a lidar sensor for three-dimensionalimaging according to some embodiments of the present invention.

FIG. 2 illustrates schematically a flexure mechanism for scanning one ormore laser sources and one or more photodetectors in a lidar sensoraccording to some embodiments of the present invention.

FIG. 3 illustrates a schematic cross-sectional view of a scanning lidarsystem according to some embodiments of the present invention.

FIG. 4 illustrates a schematic cross-sectional view of a scanning lidarsystem according to some other embodiments of the present invention.

FIG. 5 illustrates a schematic cross-sectional view of a scanning lidarsystem according to some further embodiments of the present invention.

FIG. 6 is a simplified flowchart illustrating a method ofthree-dimensional imaging using a scanning lidar system according tosome embodiments of the present invention.

FIG. 7 illustrates schematically a system for vibration management in ascanning lidar sensor according to some embodiments of the presentinvention.

FIG. 8 illustrates schematically a system for vibration management in ascanning lidar sensor according to some other embodiments of the presentinvention.

FIG. 9 illustrates schematically a system for vibration management in ascanning lidar sensor according to some embodiments of the presentinvention.

FIG. 10 illustrates schematically a system for vibration management in ascanning lidar sensor according to some other embodiments of the presentinvention.

FIG. 11 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar system that maytake into account lens field curvatures according to some embodiments ofthe present invention.

FIG. 12 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar systemaccording to some other embodiments of the present invention.

FIG. 13 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar systemaccording to some other embodiments of the present invention.

FIG. 14 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar systemaccording to some further embodiments of the present invention.

FIG. 15 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar systemaccording to some other embodiments of the present invention.

FIG. 16 shows a schematic cross-sectional view of a laser source 1600that may be utilized according to some embodiments of the presentinvention.

FIG. 17 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar systemaccording to some other embodiments of the present invention.

FIGS. 18A and 18B show schematic cross-sectional views of some exemplarylaser sources that may be utilized according to some embodiments of thepresent invention.

FIG. 19 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar systemaccording to some other embodiments of the present invention.

FIG. 20 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar systemaccording to some other embodiments of the present invention.

FIG. 21 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar systemaccording to some other embodiments of the present invention.

FIG. 22 illustrates a schematic top view of a mounting configuration foroptical components in a scanning lidar system according to some otherembodiments of the present invention.

FIG. 23 shows a schematic perspective view of the platform with theplurality of laser sources and the plurality of photodetectors mountedthereon as illustrated in FIG. 22.

DETAILED DESCRIPTION

FIG. 1 illustrates schematically a lidar sensor 100 forthree-dimensional imaging according to some embodiments of the presentinvention. The lidar sensor 100 includes an emitting lens 130 and areceiving lens 140, both being fixed. The lidar sensor 100 includes alaser source 110 a disposed substantially in a back focal plane of theemitting lens 130. The laser source 110 a is operative to emit a laserpulse 120 from a respective emission location in the back focal plane ofthe emitting lens 130. The emitting lens 130 is configured to collimateand direct the laser pulse 120 toward an object 150 located in front ofthe lidar sensor 100. For a given emission location of the laser source110 a, the collimated laser pulse 120′ is directed at a correspondingangle toward the object 150.

A portion 122 of the laser pulse 120 is reflected off of the object 150toward the receiving lens 140. The receiving lens 140 is configured tofocus the portion 122 of the laser pulse 120 reflected off of the object150 onto a corresponding detection location in the focal plane of thereceiving lens 140. The lidar sensor 100 further includes aphotodetector 160 a disposed substantially at the focal plane of thereceiving lens 140. The photodetector 160 a is configured to receive anddetect the portion 122 of the laser pulse 120 reflected off of theobject at the corresponding detection location. The correspondingdetection location of the photodetector 160 a is conjugate with therespective emission location of the laser source 110 a.

The laser pulse 120 may be of a short duration, for example, 100 nspulse width. The lidar sensor 100 further includes a processor 190coupled to the laser source 110 a and the photodetector 160 a. Theprocessor 190 is configured to determine a time of flight (TOF) of thelaser pulse 120 from emission to detection. Since the laser pulse 120travels at the speed of light, a distance between the lidar sensor 100and the object 150 may be determined based on the determined time offlight.

According to some embodiments, the laser source 110 a may be rasterscanned to a plurality of emission locations in the back focal plane ofthe emitting lens 130, and is configured to emit a plurality of laserpulses at the plurality of emission locations. Each laser pulse emittedat a respective emission location is collimated by the emitting lens 130and directed at a respective angle toward the object 150, and incidentsat a corresponding point on the surface of the object 150. Thus, as thelaser source 110 a is raster scanned within a certain area in the backfocal plane of the emitting lens 130, a corresponding object area on theobject 150 is scanned. The photodetector 160 a is raster scanned to aplurality of corresponding detection locations in the focal plane of thereceiving lens 140. The scanning of the photodetector 160 a is performedsynchronously with the scanning of the laser source 110 a, so that thephotodetector 160 a and the laser source 110 a are always conjugate witheach other at any given time.

By determining the time of flight for each laser pulse emitted at arespective emission location, the distance from the lidar sensor 100 toeach corresponding point on the surface of the object 150 may bedetermined. In some embodiments, the processor 190 is coupled with aposition encoder that detects the position of the laser source 110 a ateach emission location. Based on the emission location, the angle of thecollimated laser pulse 120′ may be determined. The X-Y coordinate of thecorresponding point on the surface of the object 150 may be determinedbased on the angle and the distance to the lidar sensor 100. Thus, athree-dimensional image of the object 150 may be constructed based onthe measured distances from the lidar sensor 100 to various points onthe surface of the object 150. In some embodiments, thethree-dimensional image may be represented as a point cloud, i.e., a setof X, Y, and Z coordinates of the points on the surface of the object150.

In some embodiments, the intensity of the return laser pulse is measuredand used to adjust the power of subsequent laser pulses from the sameemission point, in order to prevent saturation of the detector, improveeye-safety, or reduce overall power consumption. The power of the laserpulse may be varied by varying the duration of the laser pulse, thevoltage or current applied to the laser, or the charge stored in acapacitor used to power the laser. In the latter case, the charge storedin the capacitor may be varied by varying the charging time, chargingvoltage, or charging current to the capacitor. In some embodiments, theintensity may also be used to add another dimension to the image. Forexample, the image may contain X, Y, and Z coordinates, as well asreflectivity (or brightness).

The angular field of view (AFOV) of the lidar sensor 100 may beestimated based on the scanning range of the laser source 110 a and thefocal length of the emitting lens 130 as,

${{AFOV} = {2\mspace{14mu}{\tan^{- 1}\left( \frac{h}{2f} \right)}}},$where h is scan range of the laser source 110 a along certain direction,and f is the focal length of the emitting lens 130. For a given scanrange h, shorter focal lengths would produce wider AFOVs. For a givenfocal length f, larger scan ranges would produce wider AFOVs. In someembodiments, the lidar sensor 100 may include multiple laser sourcesdisposed as an array at the back focal plane of the emitting lens 130,so that a larger total AFOV may be achieved while keeping the scan rangeof each individual laser source relatively small. Accordingly, the lidarsensor 100 may include multiple photodetectors disposed as an array atthe focal plane of the receiving lens 140, each photodetector beingconjugate with a respective laser source. For example, the lidar sensor100 may include a second laser source 110 b and a second photodetector160 b, as illustrated in FIG. 1. In other embodiments, the lidar sensor100 may include four laser sources and four photodetectors, or eightlaser sources and eight photodetectors. In one embodiment, the lidarsensor 100 may include 8 laser sources arranged as a 4×2 array and 8photodetectors arranged as a 4×2 array, so that the lidar sensor 100 mayhave a wider AFOV in the horizontal direction than its AFOV in thevertical direction. According to various embodiments, the total AFOV ofthe lidar sensor 100 may range from about 5 degrees to about 15 degrees,or from about 15 degrees to about 45 degrees, or from about 45 degreesto about 90 degrees, depending on the focal length of the emitting lens,the scan range of each laser source, and the number of laser sources.

The laser source 110 a may be configured to emit laser pulses in theultraviolet, visible, or near infrared wavelength ranges. The energy ofeach laser pulse may be in the order of microjoules, which is normallyconsidered to be eye-safe for repetition rates in the KHz range. Forlaser sources operating in wavelengths greater than about 1500 nm, theenergy levels could be higher as the eye does not focus at thosewavelengths. The photodetector 160 a may comprise a silicon avalanchephotodiode, a photomultiplier, a PIN diode, or other semiconductorsensors.

The angular resolution of the lidar sensor 100 can be effectivelydiffraction limited, which may be estimated as,θ=1.22 λ/D,where λ is the wavelength of the laser pulse, and D is the diameter ofthe lens aperture. The angular resolution may also depend on the size ofthe emission area of the laser source 110 a and aberrations of thelenses 130 and 140. According to various embodiments, the angularresolution of the lidar sensor 100 may range from about 1 mrad to about20 mrad (about 0.05-1.0 degrees), depending on the type of lenses.

In some embodiments, the laser sources and the photodetectors may bescanned using relatively low-cost flexure mechanisms, as describedbelow.

FIG. 2 illustrates schematically a flexure mechanism 200 that may beused for scanning one or more laser sources 110 a-110 d and one or morephotodetectors 160 a-160 d in the lidar sensor 100 illustrated in FIG.1, according to some embodiments of the present invention. In thisexample, four laser sources 110 a-110 d and four photodetectors 160a-160 d are mounted on a same rigid platform 230. The positions of thelaser sources 110 a -110 d and the photodetectors 160 a-160 d arearranged such that each laser source 110 a, 110 b, 110 c, or 110 d isspatially conjugate with a corresponding photodetector 160 a, 160 b, 160c, or 160 d. The platform 230 is coupled to a first base plate 210 by afirst flexure comprising two flexure elements 220 a and 220 b. Theflexure elements 220 a and 220 b may be deflected to the left or rightby using a single actuator, such as the voice coil 250 and the permanentmagnet 260 as shown in FIG. 2, or by a piezoelectric actuator, and thelike. In one embodiment, the first base plate 210 may be coupled to asecond base plate 212 by a second flexure comprising two flexureelements 270 a and 270 b. The flexure elements 270 a and 270 b may bedeflected forward or backward by using a single actuator, such as thevoice coil 252 and the permanent magnet 262 as shown in FIG. 2, or by apiezoelectric actuator, and the like.

Thus, the laser sources 110 a-110 d and the photodetectors 160 a-160 dmay be scanned in two dimensions in the focal planes of the emittinglens 130 and the receiving lens 140, respectively, by the left-rightmovements of the flexure elements 220 a and 220 b, and by theforward-backward movements of the flexure elements 270 a and 270 b.Because the laser sources 110 a-110 d and the photodetectors 160 a-160 dare mounted on the same rigid platform 230, the conjugate spatialrelationship between each laser-photodetector pair is maintained as theyare scanned, provided that the lens prescriptions for the emitting lens130 and the receiving lens 140 are essentially identical. It should beappreciated that, although four laser sources 110 a-110 d and fourphotodetectors 160 a-160 d are shown as an example in FIG. 2, fewer ormore laser sources and fewer or more photodetectors may be mounted on asingle platform 230. For example, one laser source and onephotodetector, or two laser sources and two photodetectors, or eightlaser sources and eight photodetectors may be mounted on a singleplatform 230, according to various embodiments of the present invention.In one embodiment, eight laser sources may be arranged as a 4×2 array,and eight photodetectors may be arranged as a 4×2 array, all mounted onthe same rigid platform 230.

In some embodiments, a first position encoder 240 may be disposedadjacent the platform 230 for detecting coordinates of the laser sources110 a-110 d in the left-right direction (i.e., the x-coordinates), and asecond position encoder 242 may be disposed adjacent the first baseplate 210 for detecting coordinates of the laser sources 110 a-110 d inthe forward-backward direction (i.e., the y-coordinates). The firstposition encoder 240 and the second position encoder 242 may input thex-y coordinates of the laser sources 110 a-110 d to the processor 190 tobe used for constructing the three-dimensional image of the object 150.

In other embodiments, other types of flexure mechanisms may be used in ascanning lidar sensor. Additional description related to a scanninglidar sensor is provided in U.S. patent application Ser. No. 15/267,558,filed on Sep. 16, 2016, the disclosure of which is hereby incorporatedby reference in its entirety for all purposes. In some embodiments,instead of using refractive lenses for collimating and focusing thelaser pulses, reflective lenses or mirrors may be used for collimatingand focusing the laser pulses. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications.

I. Scanning Apparatuses and Methods for a Lidar System

Scanning lidars, such as those described above in relation to FIGS. 1and 2, may be susceptible to vibrations caused by the scanningmechanisms. For example, in the scanning lidar system illustrated inFIG. 2, the back and forth scanning motions of the platform 230 in theleft-right direction or the forward-back direction may cause vibrationsof the whole lidar system. Such vibrations can impair the performance ofthe lidar system. For example, three-dimensional images acquired by thelidar system may be unstable due to such vibrations. Therefore,embodiments of the present invention may employ counter-balancetechniques in scanning lidar systems for mitigating vibrations.

FIG. 3 illustrates a schematic cross-sectional view of a scanning lidarsystem 300 according to some embodiments of the present invention. Thelidar system 300 may include a fixed frame 310, a first platform 320flexibly attached to the fixed frame 310, and a second platform 350flexibly attached to the fixed frame 310. The lidar system 300 mayfurther include a lens assembly attached to the first platform 320. Thelens assembly may include a first lens 342 and a second lens 344 mountedin a lens mount 330. Each of the first lens 342 and the second lens 344may include a single lens element, or multiple lens elements asillustrated in FIG. 3. The first lens 342 may define a first opticalaxis in a first direction (e.g., in the direction of the Z-axis) and afirst focal plane (e.g., in an X-Y plane). The second lens 344 maydefine a second optical axis substantially parallel to the first opticalaxis and a second focal plane (e.g., in an X-Y plane). In someembodiments, the first lens 342 and the second lens 344 may havesubstantially the same focal length, so that the first focal plane andthe second focal plane may be substantially coplanar.

The lidar system 300 may further include an electro-optic assemblyattached to the second platform 350. The electro-optic assembly mayinclude one or more laser sources 360 and one or more photodetectors 370mounted on the second platform 350. The second platform 350 can be, forexample, a printed circuit board including electric circuits for drivingthe one or more laser sources 360 and the one or more photodetectors370. The second platform 350 may be flexibly attached to the fixed frame310 and positioned apart from the first platform 320 in the direction ofthe first optical axis or the second optical axis (e.g., in the Zdirection), such that the one or more laser sources 360 liesubstantially at the first focal plane of the first lens 342, and theone or more photodetectors 370 lie substantially at the second focalplane of the second lens 344. Each photodetector 370 may be positionedapart from a corresponding laser source 360 on the second platform 350so as to be optically conjugate with respect to each other, as describedabove.

In some embodiments, the first platform 320 may be flexibly attached tothe fixed frame 310 via a first flexure 322, such that the firstplatform 320 may be translated in a first plane (e.g., an X-Y plane)using a first actuator 382. The second platform 350 may be flexiblyattached to the fixed frame 310 via a second flexure 352, such that thesecond platform 350 may be translated in a second plane (e.g., an X-Yplane) using a second actuator 384. Each of the first actuator 382 andthe second actuator 384 may comprise a voice coil and a magnet, a piezomotor, or the like.

The lidar system 300 may further include a controller 390 coupled to thefirst actuator 382 and the second actuator 384. The controller may beconfigured to translate the first platform 320 to a plurality of firstpositions in the first plane through the first actuator 382, and totranslate the second platform 350 to a plurality of second positions inthe second plane through the second actuator 384. Each respective secondposition of the second platform 350 may correspond to a respective firstposition of the first platform 320. In some embodiments, the motion ofthe second platform 350 may be substantially opposite to the motion ofthe first platform 320, as illustrated by the arrows in FIG. 3. In thismanner, any vibration caused by the motion of the lens assembly maycancel any vibration caused by the motion of the electric-optic assemblyto certain degree. Therefore, the lidar system 300 may impart a minimalnet vibration to an external frame.

In some embodiments, the first platform 320 and the second platform 350are translated with respect to each other such that a momentum of thelens assembly and a momentum of the electro-optic assembly substantiallycancel each other. For example, the amount of motion of the firstplatform 320 may be inversely proportional to a mass of the lensassembly, and the amount of the motion of the second platform 350 may beinversely proportional to a mass of the electro-optic assembly. In thismanner, the lidar system 300 may impart a negligible net vibration to anexternal frame.

FIG. 4 illustrates a schematic cross-sectional view of a scanning lidarsystem 400 according to some other embodiments of the present invention.The lidar system 400 is similar to the lidar system 300 illustrated inFIG. 3, but may further include a post 410 attached to the fixed frame310 and a linkage member 420 attached to the post 410. The linkagemember 420 may mechanically couple the first flexure 322 and the secondflexure 352 to each other so as to facilitate reciprocal motions betweenthe first platform 320 and the second platform 350. In some embodiments,a single actuator 384 may be coupled to either the first platform 320 orthe second platform 350 for controlling both the motion of the firstplatform 320 and the motion of the second platform 350 through thelinkage member 420.

The linkage member 420 may be configured to force the first platform 320and the second platform 350 to move in opposite directions. For example,the linkage member 420 may include an arm 422 attached to the post 410at a pivot point 424, as illustrated in FIG. 4. As the second platform350 is translated through the second flexure 352 using the actuator 384,the arm 422 may rotate about the pivot point 424, which may in turncause the first platform 320 to move in an opposite direction withrespect to the motion of the second platform 350 through the firstflexure 322. The linkage member 420 may pivot about the pivot point 424by means of a bearing or a flexure attachment, which may allow pivotmotions without adding frictional losses. The arm 422 of the linkagemember 420 may also be attached to the first platform 320 and the secondplatform 350 by means of bearings or flexures. It should be noted thatalthough the actuator 384 is depicted as attached to the second platform350 in FIG. 4, the actuator 384 may be attached to the first platform320 in some other embodiments, such that a motion of the first platform320 may cause a reciprocal motion of the second platform 350 through thelinkage member 420.

In some embodiments, the linkage member may be configured such that arate of motion of the first platform 320 is substantially inverselyproportional to the mass of the lens assembly, and a rate of motion ofthe second platform 350 is substantially inversely proportional to themass of the electro-optic assembly, so that a momentum of the lensassembly and a momentum of the electro-optic assembly substantiallycancel each other. Therefore, the lidar system 300 may impart anegligible net vibration to an external frame. For example, asillustrated in FIG. 4, the pivot point 424 may be positioned such that aratio of the distance a from the pivot point 424 to the end of the arm422 that is attached to the first flexure 322 and the distance b fromthe pivot point 424 to the other end of the arm 422 that is attached tothe second flexure 352 may be inversely proportional to a ratio of themass of the lens assembly and the mass of the electro-optic assembly.

FIG. 5 illustrates a schematic cross-sectional view of a scanning lidarsystem 500 according to some further embodiments of the presentinvention. The lidar system 500 is similar to the lidar system 300illustrated in FIG. 3, but here the first platform 320 and the secondplatform 350 are coupled to each other via the actuator 382. Theactuator 382 may be configured to cause the first platform 320 and thesecond platform 350 to move in opposite directions. For example, theactuator 382 may include a voice coil and a first magnet attached to thefirst flexure 322, as well as a second magnet 510 attached to the secondflexure 352. Activation of the voice coil may cause the first platform320 to move in one direction and the second platform 350 to move in theopposite direction, as illustrated by the arrows in FIG. 5.

FIG. 6 is a simplified flowchart illustrating a method 600 ofthree-dimensional imaging using a scanning lidar system according tosome embodiments of the present invention. The method 600 may include,at 602, translating a lens assembly to a plurality of first positions.The lens assembly may include a first lens defining a first optical axisin a first direction and a first focal plane, and a second lens defininga second optical axis substantially parallel to the first optical axisand a second focal plane.

The method 600 may further include, at 604, translating an electro-opticassembly to a plurality of second positions, wherein the electro-opticassembly moves in a direction substantially opposite to motion of thelens assembly. Each respective second position corresponds to arespective first position of the lens assembly. The electro-opticassembly may include a first laser source positioned substantially atthe first focal plane of the first lens, and a first photodetectorpositioned substantially at the second focal plane of the second lens.The first laser source and the first photodetector are spaced apart fromeach other so as to be optically conjugate with respect to each other.

The method 600 may further include, at 606, at each of the plurality ofsecond positions, emitting, using the first laser source, a laser pulse;and at 608, collimating and directing, using the first lens, the laserpulse towards one or more objects. A portion of the laser pulse may bereflected off of the one or more objects. The method 600 furtherincludes, at 610, receiving and focusing, using the second lens, theportion of the laser pulse reflected off of the one or more objects tothe first photodetector; at 612, detecting, using the firstphotodetector, the portion of the laser pulse; and at 614, determining,using a processor, a time of flight between emitting the laser pulse anddetecting the portion of the laser pulse. The method 600 furtherincludes, at 616, constructing a three-dimensional image of the one ormore objects based on the determined times of flight.

In some embodiments, the lens assembly and the electro-optic assemblymay be translated with respect to each other such that a momentum of thelens assembly and a momentum of the electro-optic assembly substantiallycancel each other. In some embodiments, the lens assembly and theelectro-optic assembly may be mechanically coupled to each other via alinkage member so as to facilitate reciprocal motions between the lensassembly and the electro-optic assembly, and translating the lensassembly and translating the electro-optic assembly are performedthrough an actuator coupled to one of the lens assembly or theelectro-optic assembly. In some other embodiments, the lens assembly andthe electro-optic assembly may be mechanically coupled to each other viaan actuator, and translating the lens assembly and translating theelectro-optic assembly are performed through the actuator.

In some embodiments, translating the lens assembly may include rasterscanning the lens assembly in one dimension, and translating theelectro-optic assembly may include raster scanning the electro-opticassembly in one dimension. In some other embodiments, translating thelens assembly may include raster scanning the lens assembly in twodimensions, and translating the electro-optic assembly may includeraster scanning the electro-optic assembly in two dimensions.

It should be appreciated that the specific steps illustrated in FIG. 6provide a particular method of performing three-dimensional imagingusing a lidar system according to an embodiment of the presentinvention. Other sequences of steps may also be performed according toalternative embodiments. For example, alternative embodiments of thepresent invention may perform the steps outlined above in a differentorder. Moreover, the individual steps illustrated in FIG. 6 may includemultiple sub-steps that may be performed in various sequences asappropriate to the individual step. Furthermore, additional steps may beadded and some steps may be removed depending on the particularapplications. One of ordinary skill in the art would recognize manyvariations, modifications, and alternatives.

II. Systems for Vibration Cancellation in a Lidar System

As discussed above, scanning lidar systems may be susceptible toexternal vibrations as well as internal vibrations. According to someembodiments of the present invention, a lidar system may utilizevibration isolation mounts and active vibration management systems tomitigate effects of vibrations.

FIG. 7 illustrates schematically a system 700 for vibration managementin a scanning lidar sensor according to some embodiments of the presentinvention. The system 700 may include an external frame 710 and aninternal frame 720. A lidar sensor 730 may be attached to the internalframe 720. The lidar sensor 730 may include moving parts for scanning.For example, the lidar sensor 730 may include a lens assembly and anelectro-optic assembly, either or both of which may be translated withrespect to the internal frame 720, similar to the lidar sensorsillustrated in FIGS. 1-5. The internal frame 720 can be a housing forthe lidar sensor. The external frame 710 can be a vehicle, a drone, orthe like where the lidar sensor is utilized for three-dimensionalsensing. For example, in an autonomous vehicle, the external frame 710may be a front bumper of the vehicle on which the internal frame 720 ofthe lidar sensor 730 is mounted. The external frame 710 may also be ahousing larger in size than the internal frame 720. In some embodiments,the internal frame 720 may be attached to the external frame 710 usingvibration isolation mounts 742 and 744. The vibration isolation mounts742 and 744 may include rubber dampers, springs, or other types of shockabsorbers.

The system 700 may further include active vibration managementmechanisms. In some embodiments, the system 700 may include a firstsensor 752 coupled to the internal frame 720 for measuring residualmotions of the internal frame 720 caused by external vibrations. Thefirst sensor 752 may also be used to measure motion and vibrationresulting from the internal scanning mechanism of the lidar sensor 730.The first sensor 752 may be referred to as an internal sensor. The firstsensor 752 may comprise an accelerometer that can measure motions alongone axis, two axes, or three axes (e.g., along the X-, Y-, and/orZ-axes). In some other embodiments, the first sensor 752 may comprise adisplacement sensor, such as an encoder, a capacitive sensor, a Hallsensor, or the like.

The system 700 may further include one or more actuators 762 and 764coupled to the internal frame 720 for moving the internal frame 720 withrespect to the external frame 710. For example, a first actuator 762 maybe configured to move the internal frame 720 up or down (e.g., along theZ-axis) with respect to the external frame 710, and a second actuator764 may be configured to move the internal frame 720 forward or backward(e.g., along the X-axis) with respect to the external frame 710, asillustrated in FIG. 7. Similarly, a third actuator (not shown in FIG. 7)may be configured to move the internal frame 720 left or right (e.g.,along the Y-axis) with respect to the external frame 710. Each of thefirst actuator 762 and the second actuator 764 may comprise a voice coilmotor, a piezo motor, or the like.

The system 700 may further include a controller 790 coupled to the firstsensor 752, the first actuator 762, and the second actuator 764 Thecontroller 790 may be configured to provide “feedback” compensation forthe residue motions of the internal frame 720 caused by external orinternal vibrations. For example, the controller 790 may cause theinternal frame 720 to be translated up or down (e.g., along the Z-axis)through the first actuator 762, or be translated forward or back (e.g.,along the X-axis) through the second actuator 764, based on the amountof motion of the internal frame 720 measured by the first sensor 752.

The system 700 may further include a second sensor 754 coupled to theexternal frame 710 for measuring vibration motions of the external frame710 before such motions are attenuated by the vibration isolation mounts742 and 744. The second sensor 754 may be referred to as an externalsensor. For example, when applied in an autonomous vehicle, thevibration motions of the external frame 710 can be due to uneven roads,road noise, engine noise, and the like, as well as internal noise fromthe scanning mechanism of the lidar system. The second sensor 754 maycomprise an accelerometer that can measure motions along one axis, twoaxes, or three axes (e.g., along the X-, Y-, and/or Z-axes). In someother embodiments, the second sensor 754 may comprise a displacementsensor, such as an encoder, a capacitive sensor, a Hall sensor, or thelike.

In some embodiments, the controller 790 may also be coupled to thesecond sensor 754 and configured to provide “feedforward” compensationbased on the amount of motion of the external frame 710 measured by thesecond sensor 754. Modeling of the system response to externalvibrations and resonances may be used to control the feedforwardcorrections. Feedforward corrections are proactive, and therefore mayrespond faster as compared to feedback corrections, which are reactive.

In some cases, translational motions of the internal frame 720 may notadequately compensate for large motions caused by the vibration of theexternal frame 710. For example, when a car hits a large pot hole, thecar may have a large rocking motion in its pitch (e.g., a rotation aboutthe Y-axis). If left uncompensated, this rocking motion may cause alidar to aim upward toward the sky or downward toward the ground,instead of aiming toward the front of the car. Therefore, in someembodiments, the internal frame 720 may be tilted up or down (and/orleft or right) to compensate for such tilting motions of the externalframe 710. For example, if the first actuator 762 is positionedoff-center between the vibration isolation mounts 742 and 744, theinternal frame 720 may be tilted up or down about the Y-axis through thefirst actuator 762.

In some embodiments, the signals from the first sensor 752 and/or thesecond sensor 754 may be used for image stabilization, eithermechanically or digitally. Mechanical image stabilization for the mostpart may be achieved through vibration cancellation as described above.However, due to the complexity of mechanical vibration modes, thecontroller 790 may utilize a model or empirical approach to its feedbackcontrol in order to more effectively provide image stabilization.Additionally, signals from the first sensor 752 (and the second sensor754 if available) may be sent to an image processing unit for the lidarsensor 730. Residual errors detected by the first sensor 752 and/or thesecond sensor 754 can be used by the image processing unit to digitallyshift the image, thus providing a digital image stabilization function.

FIG. 8 illustrates schematically a system 800 for vibration managementin a scanning lidar sensor according to some other embodiments of thepresent invention. The system 800 is similar to the system 700illustrated in FIG. 7, but may further include a third actuator 766positioned apart from the first actuator 762. The controller may befurther coupled to the third actuator 766, and configured to compensatepitch motions (e.g., rotations about the Y-axis) of the external frame710 by pushing the first the internal frame 720 by the first actuator762 and pulling the internal frame 720 by the third actuator 766, orvice versa. Similarly, the system 800 may further include a fourthactuator (not shown in FIG. 8) positioned apart from the second actuator764 (e.g., along the Y-axis), for compensating the yaw motions (e.g.,rotations about the Z-axis) of the external frame 710.

According to some other embodiments of the present invention,counter-moving masses may be used for active vibration management. FIG.9 illustrates schematically a system 900 for vibration management in ascanning lidar sensor according to some embodiments of the presentinvention. The system 900 may include a counter-mass 910 movablyattached to the internal frame 720. The system 900 may further include afirst actuator 922 mechanically coupled to the counter-mass 910 formoving the counter-mass 910 along the Z-axis (e.g., up or down). Thefirst actuator 922 may comprise a voice coil motor, a piezo motor, orthe like.

A controller 990 may be coupled to the first sensor 754 and the firstactuator 922, and configured to control the first actuator 922 based onthe amount of motion of the internal frame 720 as measured by the firstsensor 754. For example, in response to the first sensor 754 sensing anupward motion (e.g., along the positive Z direction) of the internalframe 720, the controller 990 may cause the counter-mass 910 to movedownward (e.g., along the negative Z direction) with respect to theinternal frame 720, so that a net movement of the internal frame 720 maybe substantially zero. In some embodiments, the counter-mass 910 maypreferably be positioned near the center of mass of the internal frame720 including the mass of the lidar sensor 730 and other associatedparts.

In some embodiments, the system 900 may also include a second actuator924 mechanically coupled to the counter-mass 910 for moving thecounter-mass 910 along the X-axis (e.g., forward or backward). Thecontroller 990 may be further coupled to the second actuator 924 andconfigured to cause the counter-mass 910 to move along the X-axis basedon the amount of motion of the internal frame 720 along the X-axis asmeasured by the first sensor 754, so as to result in a nearly zero netmotion of the internal frame 720 along the X-axis. Similarly, the system900 may also include a third actuator (not shown in FIG. 9) for movingthe counter-mass 910 along the Y-axis.

In some embodiments, the controller 990 may also be coupled to thesecond sensor 752 (i.e., the external sensor) and configured to provide“feedforward” compensation of the external vibrations by moving thecounter-mass 910 accordingly based on the amount of motions of theexternal frame 710 as measured by the second sensor 754. As discussedabove, feedforward corrections may respond faster than feedbackcorrections.

In some embodiments, more than one counter-masses may be deployed foractive vibration management. FIG. 10 illustrates schematically a system1000 for vibration management in a scanning lidar sensor according tosome other embodiments of the present invention. Similar to the system900 illustrated in FIG. 9, the system 1000 may include a firstcounter-mass 910 movably attached to the internal frame 720, a firstactuator 922 mechanically coupled to the first counter-mass 910 formoving the first counter-mass 910 along the Z-axis, and a secondactuator 924 mechanically coupled to the first counter-mass 910 formoving the first counter-mass 910 along the X-axis. In addition, thesystem 1000 may include a second counter-mass 912 movably attached tothe internal frame 720, a third actuator 936 mechanically coupled to thesecond counter-mass 912 for moving the second counter-mass 912 along theZ-axis, and a fourth actuator 938 mechanically coupled to the secondcounter-mass 912 for moving the second counter-mass 912 along theX-axis. The system 1000 may be able to account for the fact that asingle actuator may not act in line with the center of mass of theinternal frame 720. Also, the relative movements of the firstcounter-mass 910 and the second counter-mass 912 with respect to eachother may cause a torsional motion of the internal frame 720, such as arotation about the Y-axis (i.e., a pitch motion) or a rotation about theX-axis (i.e., a roll motion) of the internal frame 720, so as tocompensate for torsional vibrations.

III. Mounting Apparatuses for Optical Components in a Scanning LidarSystem

According to some embodiments of the present invention, a plurality oflaser sources and/or a plurality of photodetectors may be mounted on aplatform in a configuration that accounts for the field curvature of alens. Field curvature, also known as “curvature of field” or “Petzvalfield curvature,” describes the optical aberration in which a flatobject normal to the optical axis cannot be brought properly into focuson a flat image plane. Consider a single-element lens system for whichall planar wave fronts are focused to a point at a distance f from thelens, f being the focal length of the lens. Placing this lens thedistance f from a flat image sensor, image points near the optical axismay be in perfect focus, but rays off axis may come into focus beforethe image sensor. This may be less of a problem when the imaging surfaceis spherical. Although modern lens designs, for example lens designsthat utilize multiple lens elements, may be able to minimize fieldcurvature (or to “flatten the field”) to a certain degree, some residuefield curvature may still exist.

In the presence of field curvature of a lens, if a plurality of lasersources 110 a-110 d are mounted on a planar surface, such as illustratedin FIG. 2, laser pulses emitted by laser sources that are positioned offfrom the optical axis may not be perfectly collimated by the emissionlens 130 due to field curvature of the emission lens 130. Similarly, ifa plurality of photodetectors 160 a-160 d are mounted on a planarsurface as illustrated in FIG. 2, the laser pulses reflected off ofobjects may not be brought into perfect focus by the receiving lens 140at the photodetectors that are positioned off from the optical axis dueto field curvature of the receiving lens 140.

FIG. 11 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar system that maytake into account lens field curvatures according to some embodiments. Alens 1110 may be mounted on a lens holder 1120. The lens 1110 may becharacterized by an optical axis 1112 that passes through the lenscenter 1114, and a surface of best focus 1116 at a distance f from thelens 1110, f being the focal length of the lens 1110. The surface ofbest focus 1116 may be curved due to field curvature as discussed above,and may be referred to as a curved “focal plane” of the lens 1110. Aplurality of laser sources 1130 may be mounted on a surface 1142 of aplatform 1140 positioned approximately at the distance f from the lens1110 along the optical axis 1112. In some embodiments, the surface 1142of the platform 1140 may have a curved shape that substantially matchesthe surface of best focus 1116 of the lens 1110, so that an emissionsurface 1132 of each of the plurality of laser sources 1130 may lieapproximately at the surface of best focus 1116 of the lens 1110. Bymounting the plurality of laser sources 1130 in this configuration,laser pulses emitted by each laser source 1130 may be nearly perfectlycollimated by the lens 1110 even if the laser source 1130 is positionedoff from the optical axis 1112.

For example, assuming that the surface of best focus 1116 of the lens1110 has a spherical shape, the surface 1142 of the platform 1140 may beconfigured to have a spherical shape so that an emitting surface 1132 ofeach laser source 1130 may lie substantially on the surface of bestfocus 1116 of the lens 1110. In cases where the surface of best focus1116 of the lens 1110 has a curved shape other than spherical, such asellipsoidal, conical, or wavy shaped, the surface 1142 of the platform1140 may be shaped accordingly.

Similarly, the plurality of laser sources 1130 illustrated in FIG. 11may be replaced by a plurality of photodetectors, so that a detectionsurface 1132 of each of the plurality of photodetectors 1130 may liesubstantially at the surface of best focus 1116 of the lens 1110. Inthis configuration, laser pulses reflected off of objects may be broughtinto near perfect focus by the lens 1110 at the detection surface 1132of each photodetector 1130 even if the photodetector 1130 is positionedoff from the optical axis 1112 of the lens 1110.

In some embodiments, a plurality of laser sources and a plurality ofphotodetectors may share a same lens. The photodetectors may be placedclosely adjacent to their corresponding lasers, such that some of thereturning light is intercepted by the photodetector. Positions either tothe side, in front of the laser, or behind the laser are possible.Because the laser beam typically has a narrow angular distribution andonly utilizes the central portion of the lens, certain lens aberrations,such as spherical aberration, may be employed to advantage to directsome returning light, from the outer portions of the lens, to thephotodetectors without overly disturbing the focus properties of theoutgoing laser beam. In an alternative design, a beam splitter may beutilized to separate the outgoing and incoming beams. This may allow thelasers and detectors to share a conjugate point of the lens withoutphysically overlapping in space.

FIG. 12 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar systemaccording to some other embodiments. Here, a platform 1240 may have aplanar surface 1242, and the plurality of laser sources (orphotodetectors) 1130 may be mounted on the planar surface 1242 of theplatform 1240. The plurality of laser sources 1130 may have varyingheights h depending on their positions with respect to the optical axis1112 of the lens 1110, such that an emitting surface 1132 of eachrespective laser source 1130 may lie substantially on the surface ofbest focus 1116 of the lens 1110. For example, for a spherical-shapedsurface of best focus 1116, the laser sources 1130 farther away from theoptical axis 1112 may have greater heights than those of the lasersources 1130 closer to the optical axis 1112, as illustrated in FIG. 12,so as to account for the curvature of the surface of best focus 1116. Asan example, each laser source 1130 (or photodetector die) may be placedin a respective surface-mount package that places the die at arespective height h above the bottom of the package. The respectiveheight h may vary depending on the position of the laser source 1130 (orphotodetector die) with respect to the optical axis 1112. The packagesare then subsequently soldered to a printed circuit board placed andpositioned so that each die is correctly located at an image point ofthe lens 1110.

FIG. 13 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar systemaccording to some other embodiments. Here, the plurality of lasersources (or photodetectors) 1130 may have substantially the same heighth. But the platform 1340 may have a surface 1342 with a stepped profile,such that an emitting surface 1132 of each respective laser source 1130may lie substantially on the surface of best focus 1116 of the lens1110.

In some embodiments, laser sources and photodetectors may be mounted ina configuration that also takes into account possible distortion andvignetting of a lens. FIG. 14 illustrates a schematic cross-sectionalview of a mounting configuration for optical components in a scanninglidar system according to some further embodiments. Similar to themounting configuration illustrated in FIG. 11, a plurality of lasersources (or photodetectors) 1130 may be mounted on a curved surface 1142of a platform 1140 so that the emission surface 1132 of each lasersource 1130 lies substantially at the surface of best focus 1116 of thelens 1110. In addition, the plurality of laser sources 1130 are tiltedat varying angles, such that a normal of the emission surface 1132 ofeach laser source 1130 may point substantially toward the lens center1114. In this configuration, laser pulses emitted by laser sources 1130that are positioned off from the optical axis 1112 may be collimated bythe lens 1110 with minimal distortion and vignetting. It should beunderstood that the term “lens center” may refer to the optical centerof the lens 1110. The lens center 1114 may be a geometrical center ofthe lens 1110 in cases where the lens 1110 can be characterized as athin lens. Some compound lenses may be partially telecentric, in whichcase the preferred orientation of the normal to the laser emission ordetector surface may not point toward the geometric center of the lens,but rather the optical center of the lens, which will typically be at anangle closer to the optical axis of the lens.

In some embodiments, a plurality of photodetectors may be mounted on aplanar surface of the platform 1140. In some other embodiments, aplurality of photodetectors may be mounted on the curved surface 1142 ofthe platform 1140, so that the detection surface of each photodetectormay point substantially toward the lens center 1114. Thus, image raysmay impinge on the photodetectors substantially perpendicular to thedetection surfaces of the photodetectors so that optimal detectionefficiencies may be achieved.

FIG. 15 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar systemaccording to some other embodiments. Here, a platform 1540 may have asurface 1542 that includes a plurality of facets with varyingorientations, such that the normal of each facet 1544 substantiallypoints toward the lens center 1114 of the lens 1110. Each of theplurality of laser sources may include a surface-emitting laser, such asa vertical-cavity surface-emitting laser (VCSEL), or a side-emittinglaser mounted in a package in an orientation such that its light isemitted vertically with respect to the package.

FIG. 16 shows a schematic cross-sectional view of a laser source 1600that may be utilized according to some embodiments. The laser source1600 may include a surface-emitting laser chip 1610 mounted on a chipbase 1620 with a leveled surface 1622. The laser source 1600 may becovered with a transparent cover 1604, and may include solder pads 1606and 1608 on chip base 1620. The laser source 1600 may, for instance, bea package that is designed to be soldered to the surface of a printedcircuit board.

FIG. 17 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar systemaccording to some other embodiments. Here, a plurality of laser sources1730 are mounted on a platform 1740 with a planar surface 1742. Theplurality of laser sources 1730 may have varying heights h and varyingsurface slanting angles depending on the position of each respectivelaser source 1730 with respect to the optical axis 1112, such that thenormal of the emission surface 1732 of each respective laser source 1730points substantially toward the lens center 1114.

FIGS. 18A and 18B show schematic cross-sectional views of some exemplarylaser sources 1810 and 1820 that may be utilized according to someembodiments. Each of the laser sources 1810 and 1820 may include asurface-emitting laser chip 1802 surface-mounted on a chip base 1812 or1822 with a slanted surface 1814 or 1824. The surface slanting angle αand the base height h can vary depending on the position of the lasersource with respect to the optical axis as discussed above. For example,a laser source positioned closer to the optical axis 1112 may have arelatively smaller slanting angle α as illustrated in FIG. 18A, and alaser source positioned farther away from the optical axis 1112 may havea relatively larger slanting angle α as illustrated in FIG. 18B. Thelaser source 1810 or 1820 may be covered with a transparent cover 1804,and may include solder pads 1806 and 1808 on chip base 1812 or 1822. Thelaser source 1810 or 1820 may, for instance, be a package that isdesigned to be soldered to the surface of a printed circuit board. Insome other embodiments, a side-emitting laser chip may also be used, inwhich case the laser chip may be oriented in the package such that itslight is emitted perpendicular to the surface 1814 or 1824.

FIG. 19 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar systemaccording to some other embodiments. Here, a plurality of laser sources1930 are mounted on a platform 1940 with a substantially planar surface1942. The plurality of laser sources 1930 may have substantially thesame height h but varying surface slanting angles depending on theposition of each respective laser source 1930 with respect to theoptical axis 1112 of the lens, such that the normal of the emissionsurface 1132 of each respective laser source 1930 points substantiallytoward the lens center 1114. As illustrated, the emission surface 1932of each respective laser source 1930 may lie substantially at a focalplane 1916 of the lens 1110.

FIG. 20 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar systemaccording to some other embodiments. Here, a plurality of laser sources2030 are mounted on a platform 1940 with a substantially planar surface1942. Each of the plurality of laser sources 2030 may be tilted at arespective tilting angle, such that the normal of the emission surface2032 of each respective laser source 2030 points substantially towardthe lens center 1114. As illustrated, the emission surface 2032 of eachrespective laser source 2030 may lie substantially at a focal plane 1916of the lens 1110.

FIG. 21 illustrates a schematic cross-sectional view of a mountingconfiguration for optical components in a scanning lidar systemaccording to some other embodiments. The lidar system may include afirst lens 2110 and a second lens 2120. The first lens 2110 has a lenscenter 2114, and is characterized by a first optical axis 2112 along afirst direction and a first surface of best focus 2116. The second lens2120 has a lens center 2124, and is characterized by a second opticalaxis 2122 substantially parallel to the first optical axis 2112 and asecond surface of best focus 2126.

The lidar system may further include a plurality of surface-emittinglaser sources 2130 and a plurality of photodetectors 2140 mounted on aplatform 2150. In some embodiments, the platform 2150 is a printedcircuit board. The platform 2150 is spaced apart from the first lens2110 and the second lens 2120 along the first direction. In someembodiments, the platform 2150 may have a surface 2152 (extendingsubstantially in the direction perpendicular to the paper, i.e., the Zdirection) that includes a plurality of first facets 2154. Eachsurface-emitting laser source 2130 may be mounted on a respective firstfacet 2154. The plurality of first facets 2154 may be positioned andoriented such that an emission surface 2132 of each respective lasersource 2130 lies substantially at the first surface of best focus 2116of the first lens 2110 and its normal points substantially toward thelens center 2114 of the first lens 2110. The surface 2152 of theplatform 2150 may further include a plurality of second facets 2156.Each photodetector 2140 may be mounted on a respective second facet2156. The plurality of second facets 2156 may be positioned such that adetection surface 2142 of each respective photodetector 2140 lies at arespective position on the second surface of best focus 2126 of thesecond lens 2120 that is optically conjugate with a respective positionof a corresponding laser source 2130. The plurality of second facets2156 may be oriented such that the normal of the detection surface 2142may point substantially toward the lens center 2124 of the second lens2120.

FIG. 22 illustrates a schematic top view of a mounting configuration foroptical components in a scanning lidar system according to some otherembodiments. Here, a platform 2250 (e.g., a printed circuit board) mayhave a planar surface 2252 in the X-Y plane (i.e., in the plane of thepaper), and an edge surface 2254 extending in the Z direction (i.e., ina direction perpendicular to the paper). FIG. 23 shows a schematicperspective view of the platform 2250 with the plurality of lasersources 2130 and the plurality of photodetectors 2140 mounted thereon asillustrated in FIG. 22. Each of the plurality of edge-emitting lasersources 2230 may comprise an edge-emitting laser source. The pluralityof laser sources 2230 may be disposed on the planar surface 2252 of theplatform 2250 as an array along an arc such that an emission surface2232 of each respective laser source 2230 lies substantially at thesurface of best focus 2116 of the first lens 2110, and its normalpointing substantially toward the lens center 2114 of the first lens2110. The edge surface 2254 of the platform 2250 may include a pluralityof facets 2256. Each photodetector 2140 may be mounted on a respectivefacet 2256 of the edge surface 2254. The plurality of facets 2256 may bepositioned such that a detection surface 2142 of each respectivephotodetector 2140 lies at a respective position on the surface of bestfocus 2126 of the second lens 2120 that is conjugate with a respectiveposition of a corresponding laser source 2230. The plurality of secondfacets 2256 may be oriented such that the normal of the detectionsurface 2142 may point substantially toward the lens center 2124 of thesecond lens 2120.

It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this applicationand scope of the appended claims.

What is claimed is:
 1. A scanning lidar system comprising: an externalframe; an internal frame attached to the external frame byvibration-isolation mounts; and an electro-optic assembly movablyattached to the internal frame and configured to be translated withrespect to the internal frame during scanning operation of the scanninglidar system, wherein the vibration-isolation mounts are configured toisolate the external frame from motions of the electro-optic assemblywhile the electro-optic assembly is being translated.
 2. The scanninglidar system of claim 1 further comprising a lens assembly including afirst lens and a second lens attached to a first platform, wherein theelectro-optic assembly includes a first laser source and a firstphotodetector attached to a second platform, the second platform beingseparated from the first platform such that the first laser source liessubstantially at a focal plane of the first lens and the firstphotodetector lies substantially at a focal plane of the second lens,and the first laser source and the first photodetector being spacedapart from each other on the second platform so as to be opticallyconjugate with respect to each other.
 3. The scanning lidar system ofclaim 1 further comprising: a first sensor coupled to the internal framefor measuring an amount of motion of the internal frame; a drivingmechanism mechanically coupled to the internal frame for moving theinternal frame with respect to the external frame; and a controllercommunicatively coupled to the first sensor and the driving mechanism,the controller configured to correct an orientation of the internalframe through the driving mechanism based on the amount of motion of theinternal frame as measured by the first sensor.
 4. The scanning lidarsystem of claim 3 wherein the first sensor is configured to measure afirst amount of motion of the internal frame along a first axis and asecond amount of motion of the internal frame along a second axissubstantially orthogonal to the first axis.
 5. The scanning lidar systemof claim 3 further comprising a second sensor coupled to the externalframe for measuring an amount of motion of the external frame, whereinthe controller is further communicatively coupled to the second sensor,and the controller is further configured to correct the orientation ofthe internal frame based on the amount of motion of the external frameas measured by the second sensor.
 6. The scanning lidar system of claim5 wherein each of the first sensor and the second sensor comprises oneor more accelerometers.
 7. The scanning lidar system of claim 5 whereineach of the first sensor and the second sensor comprises a displacementsensor selected from an encoder, a capacitive sensor, or a Hall sensor.8. The scanning lidar system of claim 1 further comprising: a firstsensor coupled to the external frame for measuring an amount of motionof the external frame; a driving mechanism mechanically coupled to theinternal frame for moving the internal frame with respect to theexternal frame; and a controller communicatively coupled to the firstsensor and the driving mechanism, the controller configured to correctan orientation of the internal frame through the driving mechanism basedon the amount of motion of the external frame as measured by the firstsensor.
 9. The scanning lidar system of claim 8 wherein the first sensoris configured to measure a first amount of motion of the external framealong a first axis and a second amount of motion of the external framealong a second axis substantially orthogonal to the first axis.
 10. Thescanning lidar system of claim 9 wherein the driving mechanism comprisesa first actuator for moving the internal frame along the first axis anda second actuator for moving the internal frame along the second axis,and wherein the controller is configured to: cause the internal frame tomove along the first axis with respect to the external frame through thefirst actuator based on the first amount of motion of the externalframe; and cause the internal frame to move along the second axis withrespect to the external frame through the second actuator based on thesecond amount of motion of the external frame.
 11. A scanning lidarsystem comprising: an external frame; an internal frame attached to theexternal frame by vibration-isolation mounts; an electro-optic assemblymovably attached to the internal frame and configured to be translatedwith respect to the internal frame during scanning operation of thescanning lidar system, wherein the vibration-isolation mounts areconfigured to isolate the external frame from motion of theelectro-optic assembly while the electro-optic assembly is beingtranslated; a counterweight movably attached to the internal frame; adriving mechanism mechanically coupled to the counterweight; a firstsensor coupled to the internal frame for measuring an amount of motionof the internal frame; and a controller coupled to the first sensor andthe driving mechanism, the controller configured to cause a motion ofthe counterweight with respect to the internal frame based on the amountof motion of the internal frame measured by the first sensor during thescanning operation of the scanning lidar system, so that a momentum ofthe counterweight substantially counterbalances a momentum of theelectro-optic assembly.
 12. The scanning lidar system of claim 11further comprising a lens assembly including a first lens and a secondlens attached to a first platform, wherein the electro-optic assemblyincludes a first laser source and a first photodetector attached to asecond platform, the second platform being separated from the firstplatform such that the first laser source lies substantially at a focalplane of the first lens and the first photodetector lies substantiallyat a focal plane of the second lens, and the first laser source and thefirst photodetector being spaced apart from each other on the secondplatform so as to be optically conjugate with respect to each other. 13.The scanning lidar system of claim 11 wherein the first sensor isconfigured to measure a first amount of motion of the internal framealong a first axis and a second amount of motion of the internal framealong a second axis substantially orthogonal to the first axis.
 14. Thescanning lidar system of claim 11 further comprising a second sensorcoupled to the external frame for measuring an amount of motion of theexternal frame, wherein the controller is further communicativelycoupled to the second sensor, and the controller is further configuredto correct an orientation of the internal frame based on the amount ofmotion of the external frame as measured by the second sensor.
 15. Thescanning lidar system of claim 14 wherein each of the first sensor andthe second sensor comprises one or more accelerometers.
 16. The scanninglidar system of claim 14 wherein each of the first sensor and the secondsensor comprises a displacement sensor selected from an encoder, acapacitive sensor, or a Hall sensor.
 17. A scanning lidar systemcomprising: an external frame; an internal frame attached to theexternal frame by vibration-isolation mounts; an electro-optic assemblymovably attached to the internal frame and configured to be translatedwith respect to the internal frame during scanning operation of thescanning lidar system; a counterweight movably attached to the internalframe; a driving mechanism mechanically coupled to the counterweight; afirst sensor coupled to the external frame for measuring an amount ofmotion of the external frame; and a controller coupled to the firstsensor and the driving mechanism, the controller configured to cause amotion of the counterweight with respect to the internal frame based onthe amount of motion of the external frame measured by the first sensor.18. The scanning lidar system of claim 17 wherein the first sensor isconfigured to measure a first amount of motion of the external framealong a first axis and a second amount of motion of the external framealong a second axis substantially orthogonal to the first axis.
 19. Thescanning lidar system of claim 17 wherein the first sensor comprises oneor more accelerometers.
 20. The scanning lidar system of claim 17wherein the first sensor comprises a displacement sensor selected froman encoder, a capacitive sensor, or a Hall sensor.